org.dellroad.hl7.llp.LLPOutputStream Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of hl7lib Show documentation
Lightweight Java library for HL7 messages
The newest version!

/*
 * Copyright (C) 2008 Archie L. Cobbs. All rights reserved.
 */

package org.dellroad.hl7.llp;

import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import org.dellroad.hl7.HL7Message;
import org.dellroad.hl7.HL7Segment;
import org.dellroad.hl7.HL7Seps;
import org.dellroad.hl7.HL7Writer;

/**
 * Writes out HL7 messages using the "lower layer protocol".
 *
 * 
 * Instances are not thread safe.
 */
public class LLPOutputStream implements HL7Writer, Closeable {

    private final BufferedOutputStream outputStream;
    private final CharsetDecoder charsetDecoder;

    /**
     * Constructor for when {@link StandardCharsets#ISO_8859_1} character encoding is to be used for all messages.
     *
     * 
     * Equivalent to: {@link #LLPOutputStream(OutputStream, Charset)
     *  LLPOutputStream}{@code (output, }{@link StandardCharsets#ISO_8859_1 StandardCharsets.ISO_8859_1}{@code )}.
     *
     * @param output underlying output stream
     * @throws IllegalArgumentException if {@code output} is null
     */
    public LLPOutputStream(OutputStream output) {
        this(output, StandardCharsets.ISO_8859_1);
    }

    /**
     * Constructor for when a fixed character encoding is to be used for all messages.
     *
     * @param output underlying output stream
     * @param charset character encoding for all messages
     * @throws IllegalArgumentException if either parameter is null
     */
    public LLPOutputStream(OutputStream output, Charset charset) {
        this(output, CharsetDecoder.fixed(charset));
    }

    /**
     * Primary constructor.
     *
     * @param output underlying output stream
     * @param charsetDecoder determines the character encoding to use for each outgoing message
     * @throws IllegalArgumentException if either parameter is null
     */
    public LLPOutputStream(OutputStream output, CharsetDecoder charsetDecoder) {
        if (output == null)
            throw new IllegalArgumentException("null output");
        if (charsetDecoder == null)
            throw new IllegalArgumentException("null charsetDecoder");
        this.outputStream = new BufferedOutputStream(output);
        this.charsetDecoder = charsetDecoder;
    }

    /**
     * Write a message using HL7 LLP framing and flush the underlying output.
     */
    public void writeMessage(HL7Message message) throws IOException {

        // Write start byte
        this.outputStream.write(LLPConstants.LEADING_BYTE);

        // Get character encoding
        final Charset charset = this.charsetDecoder.charsetForOutgoingMessage(message);
        if (charset == null)
            throw new LLPException("null character encoding returned by CharsetDecoder");

        // Write message segments
        final OutputStreamWriter writer = new OutputStreamWriter(this.outputStream, charset);
        final HL7Seps seps = message.getMSHSegment().getHL7Seps();
        final StringBuilder buf = new StringBuilder();
        for (HL7Segment segment : message.getSegments()) {
            segment.append(buf, seps);
            buf.append(HL7Message.SEGMENT_TERMINATOR);
            writer.write(buf.toString());
            buf.setLength(0);
        }
        writer.flush();

        // Write stop bytes
        this.outputStream.write(LLPConstants.TRAILING_BYTE_0);
        this.outputStream.write(LLPConstants.TRAILING_BYTE_1);
        this.outputStream.flush();
    }

    /**
     * Close this output stream.
     */
    @Override
    public void close() throws IOException {
        this.outputStream.close();
    }
}